The present invention relates to a snow making system and, more particularly, to an apparatus and method that makes snow by a fan and turbine that produces a high-velocity cooled air that atomizes water, thereby creating a stream of frozen water seeds (nuclei) and a stream of small water particles, and blowing the mixed streams across a distance to freeze and form snow.
Snow making is critical to ski resorts. This is because the amount of snow and the length of time the snow is present dictate whether a resort has financially successful or unsuccessful season. Generally, as the amount of snow increases, so does the length of time the snow is present. The longer the length of time snow is present, the longer skiers are able to use a resort. However, unpredictable weather patterns can mean poor ski conditions and financial ruin to a ski resort.
Therefore, ski resorts have long recognized the need for snow making capability. However, snow making has been capital and labor intensive. Essentially, two different systems have been utilized to make snowxe2x80x94an airless system and an air (i.e., air/water) system. Typically, in an air/water system, a ski resort contains a central air compressor and water pumping center located near the base of the resort. From the center, air and water lines run along the ski slopes. At various points of the ski slopes, provision is made for tapping into the air and water lines. In an xe2x80x9cairlessxe2x80x9d system, pressurized water lines and electrical lines (or other motorized means to power the snowmaking machine) are utilized to make snow.
One very early air/water system is simply a nozzle (i.e., snowgun) that combines high amounts of compressed air and relatively low amounts of pressurized water. The compressed air and pressurized water are simultaneously discharged from the snowgun. As the compressed air and pressurized water exit the snowgun, the expansion of air creates frozen nuclei, breaks up the water into small particles, and propels it across the slope. The cold, ambient air completes the process and causes the water to freeze into snow. However, the gun design produces relatively little snow despite the large amounts of air used. The high cost of producing the compressed air is the major drawback of this type of system.
In the airless systems, compressed air is used to a limited extent, if at all. Instead, a fan typically draws ambient air into the system housing. Downstream of the fan is an air-atomizing nozzle(s) that produces very small water particles (typically less than 50 microns) that immediately freeze to form ice nuclei (seeds), as well as water nozzles that produce water droplets. The ice nuclei and water droplets mix with the ambient air from the fan and are propelled across the slope, forming snow before it reaches the ground. Although more energy efficient than the compressed air systems, they suffer the capital cost disadvantage of having the need for a portable internal combustion engine accompanying the system or, in the alternative, an electrical distribution system across the ski slopes. They are also limited to making snow at temperatures at 26 degrees F. or colder. In addition, the large size (500+ lbs.) and complexity of these systems makes it difficult to move them (and virtually impossible with a snowmobile) and prohibits mounting on towers to take advantage of the efficiency of making snow from an elevated height.
A hybrid system employing features of both the air and airless systems is found in U.S. Pat. No. 3,945,567. Compressed air is used to drive a motor that, in turn, drives air-impeller blades. The blades draw in ambient air. Exhaust air from the motor is combined with compressed air and pressurized water to form a combined stream of very small water particles. The combined stream and the ambient air are mixed. After the mixed stream exits the apparatus, additional water is sprayed into the mixed stream, where it is thereupon converted into snow when ambient temperatures are 26 degrees F. or less. An advantage of this design is that the use of compressed air eliminates the need for electric or internal combustion motors in close proximity to the apparatus. However, disadvantages to this design include the relatively inefficient motor and, although the compressed air is relatively dry, the moisture in the air will condense out as the temperature drops and cause the motor to freeze up.
In another hybrid system, U.S. Pat. No. 4,593,854 provides a water driven turbine to drive a downstream fan to draw in ambient air. An annular air/water manifold ring is downstream of the fan. The air/water manifold supports nucleating (i.e., water atomizing) nozzles or nucleators and snowmaking nozzles positioned between the former. Air and water mixtures are discharged downstream and outside of the apparatus. A water manifold is concentric to and surrounds the air/water manifold, the former of which supports nucleating nozzles. The water manifold is not used in marginal snowmaking conditions. Some of the disadvantages to this design include: 1) any water remaining within the water turbine will freeze after shutdown and cause the turbine to freeze up, and even blowing out the system will most likely leave residual water; 2) water pressure varies greatly from the top and the bottom of the mountain (100 to 500 psi or greater), leaving little xe2x80x9cpowerxe2x80x9d at the top of the mountain; 3) nucleating/air atomizing nozzles tend to freeze up unless an external heat source is supplied. Commercially available electric-fan type snowmaking machines provide electric heaters to ensure this does not occur, but with a water-powered machine electricity is not available for this function.
U.S. Pat. No. 4,597,524 is similar to U.S. Pat. No. 4,593,854 and thus has similar disadvantages. Both are similar in that they use pressurized water to drive a fan, rather than compressed air as in U.S. Pat. No. 3,945,567. Specifically, in U.S. Pat. No. 4,597,524, air-water atomizing nozzles are positioned in the fan-induced air stream and within (or outside) a shroud that surrounds the fan. A water powered turbine drives the axial fan.
U.S. Pat. No. 4,682,729 also uses the nucleating nozzle, water droplet, fan concept of the airless system and is powered by compressed air. However, a reaction fan is used, in addition to the creation of separate zones of ice nuclei and water droplets. Compressed air is sent to the reaction fan which expands the compressed air and rotates the fan blades. The rotation of the fan blades draws in ambient air. Downstream of the reaction fan is the nucleating nozzle which is centrally disposed within the system housing. The nucleating nozzle combines the compressed air with water to expel ice nuclei into the drawn-in ambient air. Downstream of the nucleating nozzle and at the exit of the system are water nozzles that expel water droplets into the mixture of ice nuclei and drawn-in ambient air. Again, this design has the disadvantage of air-atomizing nozzle freeze up unless electrically heated. Also, this design has long slender tubing exposed to cold ambient air that will rapidly clog with ice that forms when water condenses out of the compressed air. Additionally, the efficiency of this system is questionablexe2x80x94the air/water operating ratio of 22:1 at 35 degrees F. is no better than existing air/water guns.
Additional references to snow making apparatus are found in U.S. Pat. Nos. 4,813,598 and 4,901,920.
As can be seen, there is a need for an apparatus for and method of making snow, particularly one that minimizes the need for expensive compressed air. Another need is to eliminate the provision of an electrical power distribution system, or an expensive, cumbersome internal combustion engine, to drive the snow making system. Also needed is a snow making apparatus and method that can be effectively used at higher ambient temperatures, thus increasing the number of environments in which the apparatus and method can be used. Another need is for a snow making apparatus that is not prone to freeze up during operation or shutdown without the benefit of electrical heaters. Yet a further need is for apparatus and a method of making snow to be lightweight and portable such that snow can be made on elevated structures to thereby gain efficiency/capacity, or sled mounted so that it can be easily moved from slope to slope by snowmobile.
In one aspect of the present invention, a snow making system comprises a cooling subsystem having (a) a fan that draws a first air into the cooling subsystem; and (b) a turbine that expands a second air to produce an expanded air; with the cooling subsystem combining the first air and the expanded air to produce a cooled air; and a nozzle subsystem having (a) a channel that receives the cooled air; and (b) a water injector that injects water into the cooled air such that the water is atomized by the cooled air; with the said system thereby producing frozen water in the absence of a nucleating nozzle.
In a second aspect of the invention, compressed air expanded across a turbine drives a relatively high pressure ratio fan (tip turbine fan) to effect an airflow multiplication in order to achieve a high mass-flow, high-velocity air stream, coupled with a low temperature, high-velocity air stream from the turbine. The high-velocity, low temperature (super-cooled) air from the turbine outlet is used to both break up a stream of small water particles (about 500-600 microns) into very small droplets ( less than 100 microns) and instantly freezing the particles to form snowmaking seeds (nuclei). Additional nozzles inject small water particles ( less than 1000 microns) into the high mass-flow, high-velocity air from the fan, thereby breaking up the water particles into smaller droplets (about 150-250 microns), thus eliminating the need for hydraulic atomizing nozzles and, due to the airflow multiplication, allowing for increased capacity. Mixing of the first stream of frozen nuclei with the second stream of air/water triggers snow formation in the combined flow as it is projected through ambient air.
A third aspect of the invention is anti-ice protection in the form of drip shields to keep water from entering and ice from forming in grooves/seals where it might stop the unit from rotating. The invention has the capability to angle down so that gravity forces water to flow over the drip shield and past grooves/seals that might cause freeze-up problems.
A fourth aspect of the invention is thawing capability to remove ice and snow that may build up on the snow making system. The thawing system comprises a vortex tube with compressed air source and a housing/shroud surrounding the snow making system. The vortex tube splits compressed air into a hot and a cold stream. The hot stream is directed to the housing/shroud so that the snow making system (while it is not in operation) is heated sufficiently to melt accumulated ice/snow. Additionally, this aspect of the invention may be used while the snow making machine is running in order to prevent ice from forming in critical locations.